Tsan, 36, was so badly affected by altitude sickness he had to be lifted into his sleeping bag by fellow racers at the end of the first day of the race after running at altitudes of more than 4,000 metres.

Along with competitors from 21 countries, he battled on to complete the gruelling six-day competition on Saturday and now hopes to raise more than $200,000 in sponsorship for the Society for the Prevention of Cruelty to Animals in Hong Kong.

The race was won by Taiwanese runner Lin Yi-chieh, the first athlete from Asia to win a global super-marathon event. Tsan finished about half way down the field.

In an e-mail to the South China Morning Post the night before he crossed the finishing line in San Pedro de Atacama, Tsan wrote: 'This has been one of the most challenging races for me.

'I was crippled by altitude sickness on the first day when I was running at 4,100 metres. Pounding headaches, shortness of breath, dizziness and nausea kept me at a snail's pace and I needed help from my fellow competitors just to get into my sleeping bag at the end of the day.

'This is day six and I have just completed 80km. My feet look like hamburgers, my ankles are swollen and my legs are sore. I couldn't have made it without the camaraderie of my fellow competitors.'

Tsan said the temperature had 'swung wildly' from zero Celsius at night to 37 degrees during the day.

He said the tortuous route had taken them through 'swamp-like salt-crusted mounds and ice-cold rivers in a slot canyon with 20-foot-high walls [6 metres] on either side'.

Tsan, who has previously competed in races across the Sahara and Gobi deserts to raise money for the Hong Kong Cancer Fund, trained partly by carrying a sack of rice on his back while working out on a treadmill at a gym in Causeway Bay.

But he was unable to do any intensive altitude training for the race as Hong Kong's highest point is only 800 metres.